Effects of Vessel and Water Temperatures on Direct Injection in Internal Combustion Rankine Cycle Engines

Jingtao Wu,Jun Deng,Zhilong Li,Zhijun Wu,Zhe Kang,Zhehao Zhang

doi:10.1007/s42154-018-0046-4

Abstract

This study focused on the effects of vessel and water temperatures on direct injection in internal combustion Rankine cycle engines through experimental and numerical methods. First, a study was carried out with schlieren photography using a high-speed camera for simultaneous liquid–gas diagnoses. Water was directly injected into a constant-volume vessel that provided stable boundaries. We wrote a MATLAB program to calculate spray tip penetration and cone angle from the images. For the further extension of boundary conditions, a numerical model was established and calibrated in AVL-FIRE for the thorough analysis of injection characteristics. Both experimental and numerical results indicated that injection and vessel temperatures have different effects on spray tip penetration. An increase in injected water temperature leads to shorter spray tip penetration, while the spray tip penetration increases with increasing vessel temperature. However, increased injection and vessel temperatures can both decrease the spray cone angle. Moreover, the simulation results also suggested that heat conduction is a main factor in boosting evaporation under top dead center conditions. When the internal energy of water parcels surges, these parcels evaporate immediately. These results are helpful and crucial for internal combustion engines equipped with direct water injection technology.

Highlights

Reducing environmental pollution is one of the most important research objectives for internal combustion engines
To characterize the spray process, schlieren images of highpressure direct water injection were analyzed by calculating time-dependent spray tip penetration, spray cone angle, and mean spray speed
An increase in injected water temperature led to shorter spray tip penetration, while increasing constant-volume vessel (CVV) temperature tended to increase spray tip penetration

Summary

Introduction

Reducing environmental pollution is one of the most important research objectives for internal combustion engines For this purpose, water injection technology has received much attention for several decades owing to its advanced effects, which reduce nitrogen oxide emissions and fuel consumption and enhance thermal efficiency in both diesel and gasoline engines [1, 2]. Water injection technology has a positive effect on heat capacity in the cylinder, thereby lowering the peak combustion temperature. This technology [4] leads to a significant gain in the knock-limiting ignition timing advance and decrease in the compression end temperature, as well as the temperature when the exhaust valve is open. Nicholls et al [7] used inlet manifold water injection for control of nitrogen oxides, and experimental results showed that 10% water decreased nitrogen oxide emissions by 10–20%

Methods

Results

Conclusion