【作者】 巩厅房；

【导师】 毛华永； 李国祥；

【作者基本信息】 山东大学 ， 动力机械及工程， 2009， 硕士

【摘要】 车用加热器是低温条件下发动机冷起动,车厢供暖,挡风玻璃除霜的重要辅助装置。目前国内加热器的市场状况,仍然是以客车和城市公交车以及军事用车配套为主。此领域内以15KW以上的大、中功率加热器为主。喷射雾化式加热器由于燃油跟空气混合充分,燃烧完全,热效率高,有害排放少,所以要重点研究喷雾雾化加热器来满足大功率加热的需要。本文针对目前国内使用较多的YJP-Q系列喷射雾化式液体燃油加热器进行了性能摸底试验,掌握了其基本工作规律,并对其进行了相应的改进提高。供油系统作为加热器的重要组成部分,其工作性能的好坏对加热器有重要影响。本文对YJP-Q系列燃油加热器所用供油系统进行了台架摸底试验。分析了油泵转速特性;油压特性;喷油嘴特性;进、回油管长度及管径的影响;油泵距油面高度的影响;燃油滤清器的影响。试验发现:油泵油压一定时,泵油量随转速升高而增大;油泵转速一定时,泵油量随油压增大而减小;油管过长,内径过细,会使油泵流量和容积效率下降,并使泵前真空和噪声大大上升;燃油泵泵油量随油泵距油面高度的增大而降低;所用滤清器有效过滤面积偏小,原始阻力约为行业标准的2.5倍,从而导致油泵进油口真空升高,噪音加剧。另外,对YJP-Q系列加热器进行了一系列性能试验,为进一步改进加热器提供了理论依据。试验发现存在一个最佳空燃比使加热器热功率、热效率最高;且通过试验得出了0.75USgal/h、0.85USgal/h、1.00USgal/h三种常用喷嘴对应的最佳进气量调节板开度范围;试验证明了加热器进水温度对热功率、热效率有很大的影响,二者随进水温度上升而迅速降低;试验发现在某一水流量加热器热效率最大;同时,试验还发现受换热器结构尺寸及供气量的制约,同一系列加热器并不是油嘴喷油量越大加热器热功率、热效率越高,对喷油量较大的油嘴需配用更大的热交换体及风量(风压)更大的风扇。根据市场需求在现有技术和产品的基础上对YJP-Q系列燃油加热器进行了各系统尺寸的优化设计。试验发现:燃烧筒在一定长度范围内长度越长,加热器热功率、热效率越高;而小筒则在一定长度范围内长度越短,加热器热功率、热效率越高;存在一最佳尺寸锥形罩使加热器热功率、热效率最高;燃烧筒和小筒的双层燃烧室设计起到了很好的防止通过热辐射使热量流失的作用;建议导流体轴向辅助进气孔孔径缩小为φ5.5mm。目前大多数液体型燃油加热器均采用螺旋式水腔进行换热,因该类换热器的换热面积受到制约,故热量损失较大。我们加热器课题组针对现有燃油加热器热交换器所存在的不足,设计了一种换热效率更高的带换热管的燃油加热器用热交换器。此热交换器的换热管位于燃烧器火焰筒中,一方面可以增加加热器的换热面积,充分吸收高温燃气的热能;另一方面,由于换热管直接与燃烧火焰接触,会在管内产生泡态沸腾,从而强化换热,提高加热器整体的热效率。试验结果表明新设计的热交换器对提升加热器热效率有一定效果,但由于时间及试验条件的限制试验结果并不甚理想,有待条件成熟后做进一步的试验。更多还原

【Abstract】 Vehicle heater is an important assistant facility used for cold condition engine start,carriage heating and windshield hoarfrost removing.At present, in domestic market heaters mainly serve for passenger cars,big buses and military vehicles.In this domain,big heaters with more than 15 kW heat output are popular.Because spray-type heaters have many virtues,such as, full mixed of fuel and air,complete combustion,high thermal efficiency, lower harmful emissions,we should focus on spray-type heater to meet the needs of high-power heating.Performance tests were carried out on the YJP-Q series spray-type vehicle heater grasped the basic rules of their work and did corresponding improvements to the heater.Fuel pump,as an important component of vehicle heater,its quality has a significant impact on the heater.Experimental researches were carried out on the fuel pump,which is used on the YJP-Q series spray-type heater.It analyzed the rotational speed characteristic of fuel pump;fuel pressure characteristic;fuel injection nozzle characteristic;the influence of fuel inlet and return tube and its interior diameter;the influence of the height that from fuel pump to fuel surface;and the influence of fuel filter.Results of the experiment show that:the flux of fuel pump increases along with the increase of rotational speed when the fuel pressure is constant;the flux of pump decreases along with increase of fuel pressure when the rotational speed is constant.It will make flux of fuel pump and volumetric efficiency drop,also make vacuum before fuel pump and the noise rise if the fuel tube is too long, and interior diameter is too small;because the effective filtering area of fuel filter is too small,the original resistance is about two and a half times as great as the industrial standards,it causes vacuum in the pump rise,and make noise worse.Moreover,many experiments were made with the YJP-Q series spray-type vehicle heater in order to provide a theoretical basis for further improvement of heater.The results show that there is an optimal air-fuel ratio which make the heater reach its highest thermal power and efficiency.Besides, through test the optimal opening of air intake adjustable plate were found corresponding to 0.75USgal/h、0.85USgal/h、1.00USgal/h three commonly used nozzle.It proves that the entering water temperature has a great impact to the heater thermal power and efficiency,which sharp decrease with reduction of water temperature.With the increased pump flux,heater thermal efficiency first increases and then decreases.Meanwhile,it also find that to the YJP-Q spray-type heater,it’s not the greater the fuel charge of nozzle,the higher the heater thermal power and efficiency,instead there is an optimal fuel charge value because of heat exchanger efficiency constraint.According to market demand,experimental researches were carried out on the YJP-Q series spray-type heater to optimize the system core size based on the existing technologies and products.The results show:the longer the length of the combustion tube,the higher the thermal efficiency of heater;the shorter the length of the small tube,the higher the thermal efficiency of heater; there is an optimal size of cone-shaped shield which make the heater reach its highest thermal power and efficiency,the double-layer chamber design of combustion tube and small tube has played a good role to prevent heat loss; suggesting to adjust the aperture of the baffle axial auxiliary air inlet intoΦ5.5mm.At present,the majority liquid heaters use spiral water chamber to exchange heat.It has mass heat loss because of the heat exchange area constraint.Under the endeavor of our team,we devise a more efficient heater exchanger which has heat exchange tubes,in light of the existing shortcomings of the current exchanger.The heat exchange tubes are located in the flame chamber,on the one hand,this can increases the heat transfer area of heater,and fully absorb the high-temperature gas heat,on the other hand, because the heat exchange tube direct contact with the combustion flame,this will generate bubble boiling,thus enhancing heat transfer,improving the overall thermal efficiency of the heater.Test results show that the new design of heat exchanger has a certain effect to enhance the thermal efficiency of the heater,but the test results are unsatisfactory due to time and test conditions constraints.更多还原