Zhi Wang

Zhi Wang
Tsinghua University | TH · Department of Mechanical Engineering

About

230
Publications
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Introduction

Publications

Publications (230)
Article
Ammonia is a promising carbon-free fuel for internal combustion engines. However, the low reactivity and combustion sluggishness make ammonia difficult to be used in a single-fuel way. A small amount of hydrogen addition has been demonstrated beneficial to improving ammonia’s reactivity and engine performance. To overcome the safety and cost issues...
Article
Polyoxymethylene dimethyl ether (PODEn) is a promising alternative fuel for diesel due to its high oxygen contents (>40%) and high cetane number, thereby improving the thermal efficiency and reducing the pollutant emissions caused by the internal combustion engine. This study investigated the laminar burning speeds and Markstein length for PODE3 an...
Article
The hypergolic ignition behaviors of [AMIM][DCA] (1-allyl-3-methylimidazolium dicyanamide)/furfuryl alcohol (FA) blends reacting with white fuming nitric acid (WFNA) are investigated using drop test approach. Morphology results from two high speed cameras and temperature profiles from an infrared camera are combined in analyzing the hypergolic proc...
Article
Spark induced compression ignition (SICI) is a promising method to achieve high thermal efficiency as well as a robust control of combustion. With the increase of compression ratio, the popularization of bioethanol and the development of NOx emission control technologies for lean combustion, it is easier to realize high-efficiency and clean SICI co...
Article
Full-text available
The combination of electrification and advanced dedicated hybrid engines (DHEs) has been attached with promising prospects for the abatement of fuel consumption and emissions. To explore the potential of this solution, experimental data are used from a high-efficiency DHE operated under dual-mode combustion: the lean-burn spark-induced compression...
Article
Jet ignition (JI) is increasingly deemed as a promising way of increasing engine thermal efficiency due to its faster burning velocity compard with conventional spark ignition (SI). However, as an ignition method, JI won’t change the nature of premixed combustion, knock still can happen. This paper studied knock characteristics and end-gas auto-ign...
Article
Diesel engines face a challenge on environment pollutions, especially nitrogen oxides (NOx) and particle emissions. In recent years, advanced combustion modes were developed and fuels for different physical and chemical performances were investigated. Many researches showed that naphtha fuels well suited for compression ignition engines. In this pa...
Article
The dedicated hybrid engines (DHEs) with dual-mode combustion technology can drastically reduce the fuel consumption and emissions while guarantee the power density. This paper aims to investigate the optimal control of such DHE-based plug-in hybrid electric vehicles (PHEVs) under real driving conditions, with minimum fuel penalties caused by trans...
Article
Full-text available
Strict regulations on fuel economy are driving modern gasoline engines to adopt more advanced technologies to improve thermal efficiency. Some of the technologies, for example ultra-high compression ratio and spark assisted compression ignition, will elevate the thermodynamic condition near top dead center (TDC) to a considerably high level, even u...
Article
The combustion of combustible gaseous mixture with/without oil droplet is studied based on a rapid compression machine under conditions comparable with the state at the end of compression in SI-engine cylinder. The ignition and burning processes of gaseous mixtures with oil droplet and the pressure traces for same initial state cases with and witho...
Article
Spark assistance along with oxygenated components addition is a promising method to achieve stable compression ignition, high thermal efficiency and low particle emission. To this end, ethanol blended with non-oxygenated gasoline was fueled to an engine working with spark-ignition to compression-ignition (SICI) mode under air dilution and exhaust-d...
Article
A deep reinforcement learning(DRL) based energy management strategy for hybrid electric vehicles(HEVs) of the power split type using HCCI/SI multimode combustion is proposed. First, an HEV model is established based on engine bench tests and finite element analysis(FEA) of the electirc machines. Then, considering the vehicle as the environment, a r...
Article
To explore a suitable combustion strategy for natural gas engines using jet ignition, lean burn with air dilution, stoichiometric burn with EGR dilution and lean burn with EGR dilution were investigated in a single-cylinder natural gas engine, and the performances of two kinds of jet ignition technology, passive jet ignition (PJI) and active jet ig...
Article
Spark-assisted compression ignition (SACI) has a promising potential to substantially improve engine's fuel efficiency. To this end, two exothermic stages in SACI combustion, flame propagation and auto-ignition, need to be well organized to increase control authority of bulk ignition timing especially in lean burn. In this study, three gasoline sur...
Conference Paper
Sensorless operation of generators helps to reduce the cost and volume of the auxiliary power unit (APU) system for hybrid electric vehicles (HEVs). A sensorless permanent magnet synchronous generator (PMSG) control algorithm based on the signal of the crankshaft position sensor is proposed in this paper. The high-frequency (HF) voltage injection a...
Article
Jet ignition is an efficient way to achieve lean burn of the engine and a promising strategy to meet the stringent emission regulations in the future. This paper presents a distributed gas ignition (DGI) combustion concept and realizes a DGI combustion mode using a newly designed DGI igniter. The igniter integrates a fuel injector and a spark plug...
Article
Spark assistance in homogeneous charge compression ignition (HCCI) is a promising method to improve combustion stability. Fundamental experiments were carried out in a rapid compression machine along with chemical kinetics analysis to investigate the complete combustion process of spark ignition to compression ignition (SICI) using ethanol-blended...
Article
Spark assistance for homogeneous charge compression ignition (HCCI) can control combustion phasing, improve thermal efficiency, and reduce emissions in gasoline engines. As the characteristics of flame propagation determine the control authority of ignition timing, it is important and necessary to investigate pressure dependence of flame speed in t...
Article
The ignition phenomena of stoichiometric methanol/oxygen/argon mixture are comprehensively investigated at p = 12–24 bar, T = 840–1000 K, using a rapid compression machine (RCM). A strong tendency of stochastic ignition followed by non-forcible flame propagation at a speed of ∼11 m/s is demonstrated. Such an event may be responsible for the pre-ign...
Article
Pre-chamber jet ignition is a promising combustion technology to accelerate burning velocity and improve combustion stability in natural gas engines. In this study, firstly, the ignition characteristics and the dilution limits in passive pre-chamber system with different orifice diameters were experimentally investigated based on a rapid compressio...
Article
Natural gas engines have become increasingly important in transportation applications, especially in the commercial vehicle sector. With increasing demand for high efficiency and low emissions, new technologies must be explored to overcome the performance limitations of natural gas engines such as limits on lean or dilute combustion, unstable combu...
Article
Pre-chamber jet ignition is a promising combustion technology to achieve fast combustion in natural gas engines. First, the ignition and combustion characteristics of mixtures in a pre-chamber system with different diameter orifices were studied under engine-relevant pressures and temperatures in a rapid compression machine. The tested fuels, CH 4...
Article
Polyoxymethylene dimethyl ethers, with excellent volatility and oxygen content of up to 49%, have great potential to improve engine performance and emission characteristics. In this study, experiments were carried out in a single-cylinder engine fueled with gasoline/diesel/polyoxymethylene dimethyl ethers blend fuel using multiple premixed compress...
Article
Full-text available
Spark ignition induced super-knock was generated in a rapid compression machine using stoichiometric iso-octane/O_2/N_2 mixture. In addition to the pressure traces, the combustion processes were also recorded using high-speed photography, from which the characteristics of the end-gas auto-ignition were analyzed. The effect of negative temperature c...
Article
Super-knock has been the main obstacle to improve power density and engine efficiency of modern gasoline engines. Previous researches show that the key points of super-knock are composed of pre-ignition and detonation. The former is the inducement and the latter is the root reason why super-knock could damage engines dramatically. Lots of studies h...
Article
The ceramic insulators of spark plugs in gasoline engines are especially prone to damage when deto-knock occurs. To understand the damage process and mechanism, the present work investigated the impact resistance of ceramic insulators using detonation waves as impact sources. A test device that generates detonation waves was developed, representing...
Conference Paper
Investigations on lubricating oil droplet ignition in the ambient gaseous mixture under different environmental conditions are performed based on a rapid compression machine. The oil sample here was taken from a synthesized gasoline engine oil in the market. The ambient gaseous mixture consists of iso-octane and oxygen with stoichiometric ratio, as...
Article
The ignition of lubricating oil droplet has been proved to be the main factor for pre-ignition and the following super-knock in turbocharged gasoline direct injection engine. In this paper, the ignition process of lubricating oil droplet in combustible ambient gaseous mixture was investigated in a rapid compression machine (RCM). The pre-ignition i...
Article
The double-component droplet evaporation mathematical model has been developed to describe the lubricating oil evaporation process under a high-temperature and high-pressure environment, based on one dimension unsteady droplet evaporation modeling theory. The model consists of three sub-models, describing the mass and energy balance between gas and...
Conference Paper
Full-text available
With the increase of power density of gasoline direct injection (GDI) engine, a destructive combustion phenomenon defined as super-knock has been a main factor to limit the improvement of the performance of GDI engine [1]. Main induction factor for super-knock in GDI engine is low speed pre-ignition (LSPI) caused by ignition of lubricating oil drop...
Article
Full-text available
An experimental investigation on the ignition of a single lubricating oil droplet in combustible ambient gaseous mixture was performed on a rapid compression machine, under high-temperature (1060–- 1090 K) and high-pressure (13.0–36.5 bar) conditions. The lubricating oil droplet was suspended on a thin quartz fiber tip in the combustion chamber. Un...
Article
In order to mitigate spray collapse and fully utilize the advantage of flash boiling injection in gasoline direct injection (GDI) engines, it is important to understand the flashing jet behavior and its relationship with spray collapse. In this study, n-hexane sprays discharged from a modified single-hole injector and the original five-hole injecto...
Conference Paper
Full-text available
To face future crude oil shortage and tighter regulation on pollutant emissions, pilot-ignited dual-fuel internal combustion engines operating with natural gas and a diesel fuel micro-spray is one promising approach. In order to optimize such an approach through numerical simulation, accurate detailed chemical kinetics mechanisms are needed. Howeve...
Conference Paper
基于可视化快速压缩机,开展了机油液滴在不同液滴初始体积和环境条件下诱发异辛烷-空气混合气早燃的实验研究。 在初始液滴体积为 0.1, 0.2, 0.3 μL, 初始压力为 0.3, 0.4, 0.45, 0.5 bar 的条件下,研究了机油液滴/背景混合气的着火过程及整体滞燃期变化。实验结果表明,随着液滴初始体积的减小和环境初始压力的降低,其诱发混合气早燃的效果增强。 本质上, 机油液滴诱发背景气早燃效果取决于液滴蒸发速率和背景气化学反应速率的竞争。
Article
Full-text available
The present study focuses on one mode of super-knock initiation observed in a rapid compression machine (RCM). This mode is referred to as shock wave and flame front induced detonation (SWFID). Experimental high-speed imaging and two-dimensional numerical simulations with skeletal chemistry are combined to unravel the dominant steps of detonation i...
Conference Paper
Full-text available
For multi-hole gasoline direct injection (GDI) injectors, the radial expansion of jets under flash boiling conditions could cause jet-to-jet interaction and the resultant spray collapse. To understand the mechanism and influencing factors of the spray collapse, the individual jet behavior under flash boiling conditions is important. Hence, in this...
Article
This paper is to investigate the characteristics of trans-critical propane spray compared with the flash boiling spray ejected from a multi-hole injector in a constant volume chamber by using the Schlieren and backlit imaging methods. The fuel temperature (Tf) is set from 30 °C to 120 °C, injection pressure (pf) from 60 bar to 120 bar and ambient p...
Article
The main objective of this study is to understand the mechanism of the spray collapse during flash boiling using multi-hole injectors. The spray characteristics of a five-hole gasoline direct injection (GDI) injector were investigated over a range of ambient pressures and fuel temperatures with high-speed imaging and phase Doppler particle measurem...
Article
It has been widely reported that natural gas dual-fuel combustion (DFC) can achieve much lower soot emissions in contrast to conventional diesel combustion (CDC). Thus, using low-pressure direct injection (LPDI) systems could be an alternative for current high-pressure common rail injection systems, which would significantly reduce the system cost....
Article
An approach based on regression was developed to reveal the soot volume fraction (SVF) distribution of a horizontal cross-section in an optically accessible gasoline direct injection engine, based on the quantitative data in vertical images from planar laser-induced incandescence, which was calibrated by the laser extinction method (LEM). The appro...
Article
Recent years have seen increased interest in dedicated exhaust gas recirculation (D-EGR) systems integrated with reciprocating engines. By dedicating one cylinder to operate at fuel rich conditions, hydrogen is generated for use in the remaining cylinders to optimize combustion and mitigate pollutant emissions. In this study, experiments were perfo...
Article
Biodiesel is a promising alternative fuel for diesel engines. Polyoxymethylene Dimethyl Ethers (PODE), which features high cetane number, low viscosity and high oxygen content, is often used as a fuel additive. In this study, PODE is blended with biodiesel as a major components of the fuel to improve the low-temperature flow properties and the visc...
Article
Polyoxymethylene Dimethyl Ethers (PODE), with excellent volatility and oxygen content of up to 49%, have great potential to improve engine performance and emission characteristics, especially for soot reduction. In this study, experiments were carried out in a single-cylinder engine fueled with diesel, biodiesel and BP15 (15% PODE and 85% biodiesel...
Article
Partially Premixed Compression Ignition (PPCI) and Multiple Premixed Compression Ignition (MPCI) are two high efficiency and clean combustion strategies. This paper presents an experimental investigation on the efficiency of PPCI and MPCI combustion using five gasoline-like fuels: gasoline, gasoline/ethylhexyl-nitrate (EHN) blends, gasoline/diesel...
Article
A reduced 11-component (n-heptane, iso-octane, toluene, ethanol, methanol, n-decane, n-dodecane, n-hexadecane, diisobutylene, cyclohexane and methyl-cyclohexane) chemical mechanism consisting of 178 species and 758 reactions is proposed for combustion and soot formation predictions of wide distillation fuel (WDF) covering gasoline, jet and diesel f...
Article
Dedicated exhaust gas recirculation (D-EGR) is to generate H2 via fuel-rich combustion and viewed as a potential technique to meet future emission regulations without further after-treatment. In this study, firstly, the H2/CO formation through fuel-rich combustion in a single-cylinder natural gas spark ignition engine was quantitatively characteriz...
Article
This study compares the combustion and emission performance of gasoline Homogeneous Charge Compression Ignition (HCCI) and Multiple Premixed Compression Ignition (MPCI) in a single-cylinder, intake-boosting and water-cooling diesel engine with a compression ratio of 16.7. The test fuel was commercial gasoline in China with RON of 92, and intake pre...
Article
Low Speed Pre-Ignition (LSPI), also referred to as superknock or mega-knock is an undesirable turbocharged engine combustion phenomenon limiting fuel economy, drivability, emissions and durability performance. Numerous researchers have previously reported that the frequency of Superknock is sensitive to engine oil and fuel composition as well as en...
Article
Polyoxymethylene Dimethyl Ether (PODEn, n = 3-5) is a potential alternative fuel or a green fuel additive for diesel engines, owing to the unique chemical structure (CH3O[CH2O]nCH3,) and high cetane number. In this paper, the rate constants for five reaction classes about the model molecule PODE1, including hydrogen abstraction, beta-scission of co...
Conference Paper
基于一维非稳态液滴蒸发过程,建立了双组分机油液滴在高温高压环境下的蒸发模 型,包含气相、液相和相变过程三个部分,并分析了液滴温度分布和组分质量分数在液 滴蒸发过程中的变化趋势。 在此基础上,研究了环境压力、 环境温度和液滴初始半径对 机油液滴寿命、液滴蒸发百分比、液滴温度和组分质量分数等的影响。 研究表明,高温高 压环境中, 机油液滴易形成高温热点,并可能诱发早燃。
Article
Full-text available
Knocking combustion research is crucially important because it determines engine durability, fuel consumption, and power density, as well as noise and emission performance. Current spark ignition (SI) engines suffer from both conventional knock and super-knock. Conventional knock limits raising the compression ratio to improve thermal efficiency du...
Article
Recently the performance of dual fuel strategy on multi-cylinder engines over the whole engine map has received increasing attention. This research focuses on the potential of Homogeneous Charge Induced Ignition (HCII) combustion fueled with gasoline and diesel meeting Euro V emission standard through the whole operating range using a simple after-...
Article
Full-text available
This paper proposes a method to measure the reaction rate constants in kinetically-simple pyrolysis systems using rapid compression machine (RCM) and fast sampling. The method involves first performing sensitivity analysis based on a reasonable kinetic model to identify the species dominated by a target reaction. Then the time-resolved species conc...
Article
Compared to natural gas spark-ignition (SI) combustion, dual-fuel (DF) mode could achieve higher indicated thermal efficiency (ITE). The major disadvantages of natural gas DF combustion are rough combustion at high load, high CO and total hydrocarbon (THC) emissions, and low natural gas substitution rate. In the present work, a comparison of using...
Article
This paper reviews some advanced gasoline engine combustion modes, including direct injection spark ignition (DISI), homogeneous charge compression ignition (HCCI), stratified charge compression ignition (SCCI), and multiple premixed compression ignition (MPCI). To reveal the engine knock mechanism of DISI combustion, the flame propagation and pres...