第8章內(nèi)燃機(jī)臺(tái)架性能實(shí)驗(yàn)

1、第8章內(nèi)燃機(jī)臺(tái)架性能實(shí)驗(yàn)8-1 測量與計(jì)算參數(shù)一 測量參數(shù)1 轉(zhuǎn)速n 轉(zhuǎn)速傳感器2 油耗 油耗儀3 測功器讀數(shù) 測功器 4 各種溫度、壓力5 測量環(huán)境的溫度、濕度、壓力二 計(jì)算參數(shù)1實(shí)測有效扭矩 2 實(shí)測有效功率 （kW）式中：n轉(zhuǎn)速（r/min） Me實(shí)測有效扭矩（nm）3小時(shí)耗油量GT4耗油率ge=GT/Ne8-2 測試系統(tǒng)概述一、扭矩測試儀器臺(tái)架上都采用吸收式測功器，常用的有水力測功器、電力測功器、電渦流測功器。1）水力測功器水力測功器是一種典型的吸收型測功器，它將發(fā)動(dòng)機(jī)的輸出功率轉(zhuǎn)變?yōu)闊崃肯牡簦瑫r(shí)在此過程中完成轉(zhuǎn)矩測量。水力測功器主要有轉(zhuǎn)子和定子（外殼）兩部分組成。它的基本工作原理

2、是利用轉(zhuǎn)子在充滿水的定子中旋轉(zhuǎn)所產(chǎn)生的磨擦阻力來吸收發(fā)動(dòng)機(jī)功率，同時(shí)通過與可擺動(dòng)的外殼相連的測力機(jī)構(gòu)測出轉(zhuǎn)矩。由于轉(zhuǎn)子的結(jié)構(gòu)不同，水力測功器大體上分為柱銷式、盤式和渦流式3種型式。內(nèi)燃機(jī)帶動(dòng)測功機(jī)轉(zhuǎn)子旋轉(zhuǎn), 將水?dāng)囅蛲鈬? 水與攪棒的摩擦力帶動(dòng)定子轉(zhuǎn)動(dòng)。水環(huán)越厚, 摩擦阻力越大, 相當(dāng)于外界阻力矩越大。優(yōu)點(diǎn)：結(jié)構(gòu)簡單、價(jià)廉、工作可靠、應(yīng)用范圍廣、功率儲(chǔ)備大、使用方便；缺點(diǎn)：測量精度低、排水溫度不能太高、精度依賴供水壓力穩(wěn)定性。2平衡式電力測功器其工作原理和普通發(fā)動(dòng)機(jī)或電動(dòng)機(jī)基本相同，可以將發(fā)動(dòng)機(jī)的機(jī)械功利用發(fā)電機(jī)變?yōu)殡娔?，也可用電?dòng)機(jī)把電能轉(zhuǎn)變?yōu)橥蟿?dòng)發(fā)動(dòng)機(jī)的機(jī)械能。電機(jī)的轉(zhuǎn)子和定子以磁通作為媒

3、介，轉(zhuǎn)子和定子之間的作用力和發(fā)作用力大小相等，方向相反。所以只要將其定子做成能自由擺動(dòng)的浮動(dòng)方式，便可應(yīng)用與水力測功器一樣的測力機(jī)構(gòu)或拉壓傳感器測出發(fā)動(dòng)機(jī)轉(zhuǎn)矩。分直流電力測功器、交流電力測功器優(yōu)點(diǎn)：負(fù)荷和轉(zhuǎn)速調(diào)節(jié)范圍廣、工作穩(wěn)定、使用方便、運(yùn)行經(jīng)濟(jì)性好、吸收的能力可以利用，可以反拖發(fā)動(dòng)機(jī)。缺點(diǎn)：設(shè)備費(fèi)用昂貴、占地面積大。3電渦流測功器利用渦電流產(chǎn)生制動(dòng)力矩而起制動(dòng)作用。 由電渦流測功器結(jié)構(gòu)圖可知，感應(yīng)子主要由旋轉(zhuǎn)部分和擺動(dòng)部分（電樞和勵(lì)磁線圈）組成。轉(zhuǎn)子軸上的感應(yīng)子形狀猶如齒輪，與轉(zhuǎn)子同軸裝有一個(gè)直流勵(lì)磁線圈。當(dāng)勵(lì)磁線圈組通以直流電流時(shí)，其周圍便有磁場存在，那么圍繞勵(lì)磁組就產(chǎn)生一閉合磁通。很明

4、顯，位于繞組左側(cè)的感應(yīng)子具有一個(gè)極性，右側(cè)具有相反的極性。旋轉(zhuǎn)時(shí)，由于磁密值的周期性變化而產(chǎn)生渦流，此渦流產(chǎn)生的磁場同產(chǎn)生它的磁場相互作用，從而產(chǎn)生與被試機(jī)反向的制動(dòng)力矩，使電樞擺動(dòng)，通過電樞上的力臂，將制動(dòng)力傳給測量裝置。DW系列電渦流測功器特性曲線表示測功器在不同轉(zhuǎn)速下所能吸收的功率范圍，它由OABCD組成。AB最大扭矩線，當(dāng)最大扭矩為常數(shù)時(shí)所能吸收的最大功率，隨著轉(zhuǎn)速的增加而上升，在A點(diǎn)達(dá)到扭矩強(qiáng)度所能允許的最大功率。BC最大功率線。測功器達(dá)到最大扭矩點(diǎn)（A）后，隨著轉(zhuǎn)速的變化測功器所能允許吸收的最大功率。CD最高轉(zhuǎn)轉(zhuǎn)速線。測功器在工作時(shí)允許的最大轉(zhuǎn)速。 上述三段限線所包圍的區(qū)域?yàn)闇y功器

5、的工作范圍。凡動(dòng)力機(jī)或機(jī)械設(shè)備的特性在OABCD所包圍的范圍內(nèi)者均能用該型測功器進(jìn)行特性試驗(yàn)。用主戶在選用測功器時(shí)須留有余地。二、耗油量測試儀器可以分為容積式、質(zhì)量式和重力式：以小野公司的油耗儀為例！Volumetric Flow DetectorsFour pistons are arranged radially in the flow detection unit, and move back and forth repeatedly according to the flow of fluid from the inlet to the outlet. The pistons are

6、rotated by the crankshaft, and their movement is transmitted to the magnetic-coupled rotation detection unit. The rotary encoder mounted on the rotation detection unit generates pulse signals in accordance with the amount of piston movement.Wide measurement range thanks to a flow rate ratio of 1:400

7、 or more Capable of compensating for errors caused by pulsating or backflow by means of a function for detecting the direction of rotationHigh reproducibility and high-speed response result in superb reliabilityCapable of simultaneous measurement of temperature and pressure during flow rate measurem

8、ent (FP-2240HA/2250A)Gravity Flow DetectorsIf the fluid level falls below L3, the pressure signal generated by the detector causes the solenoid valve V1 to open and more fluid to flow in. When the fluid level reaches L2, valve V1 closes. Measurement of the flow rate starts after the specified time f

9、or the surface of the fluid to reach the fixed level has elapsed. As the fluid level falls from L2 as it is being consumed, the output from the differential pressure transducer changes in accordance with the gravity of the consumed fluid, and the gravity flow rate is obtained from this changed amoun

10、t.Alarms are generated if the fluid reaches the L1 overflow level or falls to the L4 insufficient fluid level.High-accuracy flow rate measurement over a wide range Built-in air extractor function to counteract the mixing in of air bubblesAlarm function to warn of overflows and low fluid levels Densi

11、ty corrections due to changes in the temperature are no longer required.Increased pressure and pressure feed are available as options.Mass Flow DetectorsThe fluid that entered from the inlet passes through the tube and goes out through the outlet. With this flow meter, the application of its inheren

12、t vibration to the tube causes a movement equivalent to the angular velocity, thereby generating a Coriolis force. As shown in the figures above, since the tube for which the Coriolis force is being generated generates a twist proportional to the mass flow rate, the mass flow rate is calculated from

13、 the amount of this twist.Continuous measurement without being affected by temperature, pressure, or densityHigh measurement accuracy (up to a ratio of 40:1 within 0.1% of the reading accuracy)Density measurement enabledThe case provided with each detector is capable of purging internal air.其他：三、轉(zhuǎn)速測量五、測量方法一 速度特性 節(jié)氣門或油門開度固定不動(dòng)，內(nèi)燃機(jī)運(yùn)轉(zhuǎn)，油溫、水溫達(dá)正常值。設(shè)定測定為速度特性測定，然后調(diào)整測功器負(fù)荷, 使轉(zhuǎn)速達(dá)到預(yù)定值, 測量計(jì)算GT、ge、Ne和Me，在特性曲線圖上標(biāo)出該點(diǎn)。再調(diào)節(jié)測功器負(fù)荷，使轉(zhuǎn)速達(dá)