Rumus-Rumus Motor Diesel

Rumus-Rumus Motor Diesel

I. Daya Motor

                a). Daya indicator 

                (Pi) = 0,785.D².S.Z.pi.n.100 (2tak)

 (Pi) = 0,785.D².S.Z .pi.n.50  (4tak)

                b). Daya efectif   

 (Pe) = 0,785.D².S.Z.pe.n.100 (2tak)

                                 (Pe) = 0,785. D².S.Z.pe.n.50  (4tak)

                c). Daya Gesekan mekanis:

                                Pf = Pi – Pe ( 2tak & 4tak)

                d). Tekanan Gesekan:

                                pf = pi – pe  (2tak & 4tak)

Ket:

                PI = Daya indicator (ikW)

                Pe = Daya Effective (ekW)

                Pf = Daya gesekan (kW)

                pf = Tekanan gesekan (bar)

                D = Diameter Silinder (m)

                S = Langkah torak (m)

                Z = Jumlah silinder

                pi = Tekanan rata2 indikator (bar)

                pe = Tekanan rata2 efektive (bar)

II. Randemen2 untuk motor (2tak & 4tak)                                    

ηth  =         1            .           

                               bi. NO                                    

ηm = .Pe . = pe = bi  = ηtot           

           Pi      pi      be    ηth

ηtot =      1       .

             be . NO      

NO = 340C + 1200 {H .     0  .} + 105S

                                            8

Ket:         ηth           = Randemen Thermis (%)

                ηm            = Randemen Mechanic (%)

                ηtot         = Randemen Total (%)

                be         = Pemakaian BB specific (kg/ekWs)

                bi = Pemakaian BB specific (kg/ik Ws)

                NO = Nilai opak (pemb.) BB (kj/ kg bb)

                C,O,S,  = Komposisi BB tdk dlm %

III. PEMAKAIAN BBM

                B = bi.PI = be.Pe (2tak & 4tak)                     

                Binj = bi.Pj = be.Pe =   B   .      (2tak)

                         Z . n   Z . n     Z . n                            

                Binj = bi.Pi.2. =be.Pe.2. = B.2. (4tak)

                        Z . n       Z . n       Z . n

                Vinj = Binj.   (2tak & 4tak)

                             γ b

           Ket:

           B   = Pemakaian BBM (kg/det)

         Binj                = Peakmakaian bb. Tiap injkecsi tiap       

                    Silinder (kg/sil/proses kompressi)

         Vinj                = Vol. inj. bb (cm³,Dm³)

          γ bb               = Berat jenis bb (kg/dm³atau grm/ cm³

                           atau ton/jam)

IV. PERBANDINGAN KOMPRESSI (Є)DAN

      DERAJAT PENGISIAN(dp)

                    Є =   (Vs – Vx) + Vc

                             Vc

                dp = (Vs – Vs) + Vc

                                   Vs

Ket : Vs = Volume langkah (m³)

          Vx = Volume awal Kompresi  (m³)

          Vc = Volume ruang rugi (R.bakar) (m³)

V. KECEPATAN TORAK (2tak & 4tak)

a. Kecepatan rata2 torak ( vp)

Vp = 2.S.n    (2tak & 4tak)

b. Kecepatan sesaat torak (Vpλ)

Vpλ = ω.R.(sin λ + R . cos 2 λ) m/s

                   2.L

  Þ ω = 2.Π.n              

           Vpλ = 2.Π.n.R.(sin λ +  R . cos 2 λ) m/s

                           2.L

c. Percepatan torak (a)                          

a λ =        ω².R.(cos λ +  R . cos 2 λ) m/s

                         L                                       

a λ = (2.Π.n)².R.(cos λ + R  . cos 2 λ) m/s

                              L

d. Jarak yang ditempuh Torak

     setelah Engkol bergerak λ^o derajat     (Sλ)                                                                 

Sλ = R (1 – cos λ) + ( R²  . sin λ)                                       

                                     2L

Ket: V     = kecepatan rata2 torak (m/s)

         S = langkah torak (m)

         N = putaran (Rps)

         λ = sudut engkol ( derajat )

         R = jari2 Engkol (m)

         ω = Kecepatan sudut (radian)

                 ÞΠ = 3.14, n = Rps

VII. NERACA PANAS                          

G_udth =  100  { 8 . C + 8 H – 0 + S }

               23       3

G_udpr = f_u.G_udth = dp.0.785 D².S.p_ud.γ_ud.  273                                                                                                                                                                                                                                                                                                                                        

                                                                    273+t_ud

G_gas = G_udpr. G_bb

Q_gas = G_gas. pj _gas.t _gas

Q_ap = 100% - (ηth + Q_gas + Q_rad )

Q_ges.mek  = Q_sil – Q_poros = ηth.- ηtot = Pi – Pe

Q air.B.NO = G_air.pj_air.∆t_air                                                                     

Kapasitas pompa = Q_air

                                 γ_air

Ket:        

 G_udth = berat udara theoritis kg/kg bb

C,H,O&S= Komposisi BBM (dlm %)

G_udpr = Berat udara praktis kg/kg bb (kg/sil,kg/proses compressi.)

f_u = faktor udara 

VI. WAKTU PEMBUKAAN DAN PENUTUPAN

       KATUP ( t  )              

                t = .  λ .  ( 2tak & 4tak)

      360.n