The internal combustion Rankine cycle (ICRC) engine utilizes pure oxygen as the oxidant instead of air during combustion to prevent the generation of nitrogen oxide emissions and lower the cost of CO2 recovery. To control combustion intensity and increase efficiency, water injection technology is implemented as it can increase the in-cylinder working fluid during combustion process. To further enhance the system thermal efficiency, the injected water is heated using coolant and waste heat before being directly injected into combustion chamber. The main challenge of controlling the ICRC engine is the interaction between water injection process and combustion stability. Ion current detection provides a potential solution of real-time detection of in-cylinder combustion status and water injection process simultaneously. In this paper, the characteristics of ion current signal in an ICRC engine were studied. The results indicate the ion current signal is primarily affected by the combination of trapped water vapor injected in the last cycle and in-cylinder combustion intensity. The water vapor contributes to the ionization reactions, which lead to enhanced ion current signals under water cycle. The ion current signal is capable of reflecting the operating conditions of the in-cylinder water injector. The phase of the ion current peak value has a linear relation as the water injection timing is delayed, and ion current detection technology has the potential to detect the combustion phase under different engine loads in an internal combustion Rankine cycle engine.

Based on the high flux synchrotron X-ray of the Shanghai Synchrotron Radiation Facility (SSRF), high precision 3D digital models of diesel nozzle tips have been established by X-ray micro-tomography technology, which reveal the internal surfaces and structures of orifices. To analyze the machining precision and characteristics of orifice processing methods, an approach is presented based on the parameters of the internal structures of nozzle orifices, including the nozzle diameter, the orifice inner surface waviness, the eccentricity distance and the angle between orifices. Using this approach, two kinds of nozzle orifice processing methods, computerized numerical control drilling and electric discharge machining, have been studied and compared. The results show that this approach enables a simple, direct, and comprehensive contrastive analysis of nozzle orifice processing methods. When processing a single orifice, the electric discharge machining method has obvious advantages. However, when there are multiple orifices, the error levels of the two methods are similar in relation to the symmetry of distribution of the orifices.

Accurate control of both the timing and quantity of injection events is critical for engine performance and emissions. The most serious problem which reduces the accuracy of the control operation in such systems is a time delay of the responsiveness for the opening and closing operation of the electromagnetic valve. Modern electronic control systems should be capable of driving high speed solenoid injectors at a very fast switch frequency with high efficiency and acceptable power requirements. In this paper, the dynamic characteristic of a high speed servo-hydraulic solenoid injector for diesel engine, with different driving circuits and control methods, is investigated. A pre-energizing control strategy based on a dual power supply is applied to speed up the opening response time of the injectors. The effect of free-wheeling circuit on the closing response time is experimentally studied and a reverse-energizing circuit is utilized for achieving a rapid extinction of the operating magnetic field. The solenoid current is measured to get the electrical delay of the injectors. Meanwhile, high-speed photography is employed to detect the total delay (electrical delay, hydraulic delay and mechanical delay) of the injection spray process. The results show that, there is a high correlation between the opening delay and the solenoid current, but the armature of the injector will not move until the current reaches a threshold value. The switching time (both the opening and the closing time) could be further optimized through the proposed driving circuits and control strategies without any change to the injectors. As a result, the interval between two injections can be significantly reduced, which can provide greater flexibility for multi-injections strategies.

Internal combustion Rankine cycle (ICRC) concept implements oxy-fuel combustion, direct water injection (DWI), and waster heat recovery (WHR) into traditional Otto or diesel cycle to realize high thermal efficiency and low emission powertrain. In order to support ICRC realization, this paper is dedicated to investigate the feasibility of implementing oxy-fuel combustion into diffusion combustion which provides fundamental information for future compression ignition (CI)-ICRC engine. The prototype oxy-fuel diffusion combustion engine test bench is established based on a retrofitted diesel engine, and the O2/CO2 mixture intake system, high-pressure common rail fuel injection system, and high-performance electronic controller are designed and installed within engine test bench to investigate the combustion and emission characteristics under different intake oxygen fractions (OF), fuel injection durations, and fuel injection timing. The optimum intake OF and fuel injection strategies are acquired within the selected experimental conditions, a 41.1% brake thermal efficiency (BTE), and 1.2% coefficient of variation (CoV) is achieved utilizing 55% intake OF, 0.7 ms fuel injection duration and 352 °CA (after exchange top dead center (TDC)) fuel injection timing. The oxy-fuel diffusion combustion proved to be a feasible solution for simultaneously reduction in NOX and particulate emissions, and NOX emissions lower than 90 × 10−6 with particulate matters (PM) around 0.1 filter smoke number (FSN) is observed during engine bench testing. The result of this study provides fundamental information for future CI-ICRC prototype engine establishment and optimization, which also could be utilized as reference guidance for potential industrialization of internal combustion engine (ICE) with oxy-fuel combustion mode.