The Beard-Pennock Variable-Stroke Compressor

A new Lyp<~ of variable-stroke c·o"'rressor, he1Jceforth referred to as the Beard-Pennock compressot•, is presented in this papc1·. Th" stroke is ~.djusted by changing Lhe lengLll of the ground link using a.n auxiliary mcclnllti;,m. AJjustin[\ Lhe ground link, dta.nges Lhe rotation angle and the el\cctiv~ lengtL of' tl1e <:ounecting rod, which in Lurn controls the pumping volume of the compresso1·. TlH' p11rnpin~; action is caused by the motion of Lhe piston which oscillates rela.tive to thu frame· '" lhc input crank rotntes through a compleLc cycle. The moLion ol' the pisLon induces a LJ·o.n;verNe force and a. bending moment in Lhe connecting rod buL no axial force or static buckling load. Since swirl combu,tion is known to improve thermal efllciertcy, the Rea.rd-Pennock varia hle-eLroke comprc,sor wag d"signed Lo induce high swirl raLe~. A complete kinewnLit and ckeJ· fout·-ba r which essentially lw d a. fixed-stroke and compression ratio but could be modi liN! Lo ]J, v" a.n adju"t" ble-sLrok<> a.nd compression ratio. In conv~ntional fixlllhll,(,ion engines, til~ powe1· is controlled hy Lhrottling the inlet which imp,irs Lhc cngin<' <•llkierH·y. However,"" adjusLable-stroke cngin~ ha.s the potential to reduce !\tel <:<)llSI.tmpl.ioC\. Siq;la anrl Siewert [SJ, for example, ,·eported fuel cconorny improv(~!nenLs raug,ing from 2-20 pcrccnL; depending upon the frictional losses and tile vehicle powcr-Lo-weighL 1·aLio, [01' au adjusln bl<:-sLroke engine ove1· a Jixed-sl.wlce engine for p:nticubr applica tiorw. 1'he firsL pat.enL' !'or ad.jusLablc--,Lr<>ke eul!;im·' nnd comwessors d>JLes back Lo Lhy Selrir,hi. [7]. In th0 design of' varia hie-stroke <:owpressor", Welsh a.nd 1\il<>y [!l[ ""'' " swn"ll pla.tc ckHign to vary the displacement, while Pouliot et ;,J. [1>[ employ " Jn~<"h>lnic:~l linkage which keeps Lhe compr<»~ion ratio approximately constn nl .. rvlo1·0 rrcrntly, i"J'<'tl variablc·-strokc JlH'rhanisms used for intci'Ilal-combust.ion engines. They arriveJ at an innovative JtJechnni>tn (.h:Li, clmnl',es tl1c oLroke whik the cotnpJ·esoioo ratio sLays almosL consLauL a11d Litis llJ<'clwni'm l'<>ccived a paLenL (U.S. 1-'aLertL No. 4,270,~95; 1981). A variation on a oLrokc clmuging mctl1n ni'm iB th~ A VCIH :JG0-2 diesel engine [2[ where, the piston changes height via hy <:Oil11H<>'~OI' holds much pnnnisc, the prob!<•rns associated with high Hlll'face-t<>-vollll\J(' r;d,io or Lli<' combusL\on ck1Trtbrt• a L minimum stroh·, increased [l'iction, t'Nlnccd ma.xinnnn Hpectl, n1trl inc•·~'""d weighl lt~tvc yel to be f11lly cv81u3ted. A possible applica Lion is to twe Lhc V>t l'i<' blc-sl.rokc mechanism, in conj J!ncLion with a digital valving system, l'or n poHitioning dev'".''· For example, the '"ljustnbl0 ,wnsh plai.c pumps preseJltly used for rna chill(' lool <:Olll.1·ob nn; devices ol' !.hie lyp<'· In Utis paper, we Jll'esonL n trJedHclli~ru wiLh an adjustabi<'·SLroke LhaL could lw used as B tOIIlpreSflOI·, ~~~ .<-l [}UIIlp 1 or £IS an DIIR"itn' [l,S]. f 1'or f'OJlVCTJicnce W0 wiJf rerer to tlw !ll<'Chanisrn as the l.lcard-Pennoek vndnblt'-s!.rokc ""'"I"'<"'Sor, for wltich a pntenL is pendin!\. Sowe of the rnajor advantages :JKsociaLHl wiL!J Lho U,•;, ,-d-Pcnnock vn ri" blc"sLroke cornprcsso1· ar<': 1. Th.e COIIlJ)("CS'Sion raLio can he ndjw;L(~d rrom ~l desired Iinit0 value Loan infinit,(~ value. 2. By plnd11g pockl'Ls on opposite sid•·s of th~ pi•Lon, Lite c;ompression and <'xpausion of the gas in Lhe di!Ierent poekcLs can Lake place at tlw snrne l,itw•. ;;_ TllCre arc no <1.xial forces or sta Lie buckling, loads a ding on the conncding rod. cJ. The vnl'iablt·-strokr· "'""P""'"'" call be manufactuJ·ecl using sLandard machine Lools. KINIIM.A TIC ANAL '{.SJS A schema Lie diagtam or Lille rhea rd-l'enuock varla ble-sttokte C()J)lpressor is shown ilJ Fig. La. The purnp·u,g >tdiou ·"produced by 1.!1c oscillating ,not:"'" of Lhc piston (link '') relative to the fram~ (link 5) os t.hte inptli. <'r>ln)< (lird, 2) rotates Lbt·ollglt n complete cycltl. Tlw ,l,roke of the compressor i" adjusLe<l by cho.Jlf'ing the lengLh of LlHl ground link (link 1). This is accomplishcu by moving Ll1e frame along the .X-axis by an ouxiliary mechanism nt,J,adtcd Lo Lhe frame (not shown ill Ll1e ligure). Moving Llte frame in Lhe positive X-direcLion increases Lhe cHective length of the conneeLing mel (link 3) and decreases the amount of roLation of the pisLon which in turn decreases Lhe compr·ession raLio and Lhe swept volume.